1. Field of the Invention
This invention relates to methods for the introduction of medication to specific points in the body. More particularly, the present invention relates to an improved apparatus and method for selectively delivering medication to a specifically targeted wall section of a blood vessel, body cavity, or the like, so as to allow more accurate medication of specific ailments.
2. State of the Art
There are a wide variety of known methods for introducing medication into the body, such as injestion, hypodermic injection, transdermal application, inhalation, and intravenous injection. However, all of these methods result in systemic drug introduction. This is appropriate for many conditions, but not in others. In certain circumstances, it is desired to introduce a drug only at a specific site of an ailment within the body. In such cases, systemic drug introduction results in substantial overmedication in order to ensure that a sufficient dosage is available at the site of the ailment. This results in the unnecessary use of excess medication, and may also exacerbate side effects.
To address some of these problems, venous catheters and similar devices have been used to introduce medication at a specific site within a blood vessel, body cavity, or the like. The catheter is threaded through the anatomy to a point near to or at the site of a specific ailment, whereupon the medication is released from the catheter. This method, however, presents several drawbacks. In a flowing blood vessel, the medication is quickly drawn downstream from the intended application site. Thus, while medication will be available at the desired site, additional medication will flow systemwide, presenting the same drawbacks as in the case of systemic medication mentioned above. In other applications, a balloon catheter or other device may be used to stop blood flow in the vessel to prevent the medication from being swept systemwide. However, because blood flow can only be stopped for brief periods of time without causing damage to surrounding tissues, this method is not satisfactory for most applications.
To address these problems, devices have been developed which attempt to place medication at a targeted site and hold it there for an extended length of time without interfereing with blood flow. In some of these devices, a drug delivery apparatus is held in place within a vessel by means of barbs or other protrusions which extend out and grab the vessel wall. These devices are undesirable because of the trauma that they cause to body tissue. Another approach of prior art devices is shown in FIG. 1. This device utilizes a thin, inflatable coil tube, denoted generally at 2, having impermeable webbing 4 disposed between several of the coils 6 at or near the distal end 8 of the device. The distal portion 8 of the tube 2 is held against the sides of the blood vessel 10 by pressurizing the coil tube, and a medication supply tube 12 delivers medication to the space 14 between the webbing 4 and the vessel wall 10. This device may thus be held in contact with the vessel wall for an extended period of time, while blood flows essentially uninterrupted through the central lumen 16 of the coil. However, the device of FIG. 1 also presents several drawbacks. First, it does not isolate the space 14 from the blood flow lumen 16 very wellxe2x80x94i.e., it leaks. Additionally, the central lumen 16 may not be large enough to accommodate the necessary blood flow. Finally, the device is complicated and expensive to manufacture.
There is thus a need for an a traumatic method of selectively introducing medication into a wall section of a body cavity, blood vessel or the like that allows the medication to remain in contact with the anatomy for an extended period of time as required, without causing trauma to body tissues, requiring the stoppage of blood flow, or resulting in needless systemwide introduction of medication.
It is therefore an object of the present invention to provide an a traumatic apparatus and method for selectively delivering medication to a target location of a body cavity, blood vessel, or the like that does not result in significant quantities of the medication being swept downstream and introduced into the body systemwide.
It is another object of this invention to provide an apparatus and method for selectively delivering medication to a target location of a body cavity, blood vessel, or the like that does not stop the flow of blood or fluid within the anatomy in order to give the medication time to be absorbed.
It is another object of this invention to provide an apparatus and method for selectively delivering medication to a target location of a body cavity, blood vessel, or the like that allows the medication to circulate through the device so as to provide a constant concentration of the medication at the vessel/device interface.
The above and other objects are realized in an apparatus comprising a compressed hollow cylinder of permeable, expandable foam, attached to the distal end of a delivery device such as a catheter or catheter guidewire. The delivery device is for introducing the compressed cylinder into the patient""s anatomy, whereby the compressed foam cylinder may be advanced to a point adjacent to a target location where medication is needed. The compressed foam cylinder is provided with means for expanding it within the body cavity, blood vessel, or the like, so as to contact the walls of the body cavity, blood vessel, or the like with its outside surface so that a medicament may be placed in contact with the walls of the patient""s anatomy, while allowing the patient""s bodily fluids to freely flow through the central hollow or lumen of the cylinder. The cylinder is provided with means for perfusing it with a medicament, such as an infusion tube which extends along the delivery device, and terminates at its distal end within the foam material, whereby medicament may be introduced into the proximal end of the infusion tube and may be released from the distal end to perfuse into the foam material. The apparatus may also be provided with a second lumen for withdrawing or circulating the medicament from or through the foam. This greatly reduces spillage if the fluid is removed from the medicament delivery volume at the same rate as it is infused into it. The apparatus is also provided with means for preventing the medicament from entering the patient""s bloodstream.
In one embodiment, the foam cylinder is compressed by means of a sheath disposed thereabout, and the means for expanding the cylinder within the patient""s anatomy comprises one of various means for opening and pulling the sheath off of the foam cylinder. In an alternative embodiment, the sheath is soluble in water or other fluid so that it breaks down within the patient, thereby allowing the hydrophillic foam cylinder to expand. In still another embodiment, the medicament is preloaded into the foam material and released when the protective sheath is removed from the foam cylinder.
These and other objects are also realized in a method for selectively delivering medication to a target location of a body cavity, blood vessel, or the like comprising the steps of obtaining an apparatus for delivering said medicament as described, introducing the apparatus into the anatomy of the patient, directing the apparatus to an anatomical location in need of medicament, expanding the cylinder within the patient so as to contact the walls of the body cavity, blood vessel, or the like with the outside of said foam cylinder, while allowing the patient""s bodily fluids to freely flow through the central hollow of said cylinder, delivering a medicament to the target location by perfusing the medicament into the foam material, and allowing the medicament impregnated foam to remain in contact with the walls of the patient""s body cavity, blood vessel, or the like for sufficient time to be absorbed thereby, and then removing the apparatus from the patient""s anatomy following use.
These and other objects are also realized in a method for manufacturing said apparatus.
Other objects and features of the present invention will be apparent to those skilled in the art, based on the following description, taken in combination with the accompanying drawings.